松辽盆地徐家围子地区深反射结构及其盆地动力学意义

Reflection feature and geodynamic significance of deep seismic reflection in Xujiaweizi region of north Songliao basin,China

通过松辽盆地徐家围子地区深反射地震剖面与世界典型深反射剖面对比,以岩石圈流变学模型为基础,结合浅层钻探资料可以发现,松辽盆地与世界典型裂谷盆地有相似的深反射特征,即层状结构十分明显。岩石圈横向分段性是另一个显著特点,由中下地壳挤压"断裂带"和由热流底辟体组成的"岩浆底辟带"分开。下部块段控制上部层状构造体系的形成与演化过程。由此证明,裂谷演化过程中地幔上涌是主要动力。地壳"三明治结构"和热流底辟体的发育表明,盆地不仅有高热流的地质条件,而且深部存在无机物质"储库"与通道。

The Xujiaweizi depression is a typical district of the Songliao rift. The seismic reflection feature of the Xujiaweizi deep reflection in the north Songliao basin is similar to that of a typical rift deep reflection in the world. It has both sandwich structure in the crust and the bright reflection on the mantle of the lithosphere, which indicates the decoupling between the crust and the mantle of the lithosphere. The detachment belt between the upper and middle crusts, the roof of the middle crust, and the MOHO are three strong reflection layers. Another obvious specialty is that the lithosphere is divided into several segments laterally by the compressing faults in the lower-middle crust and the diapirs composed of hot fluid-diapir （or magma） bodies. The gurgitation of the detachment surface and fault system in the upper crust detachment surface is controlled by the hot fluid diapir and the splice structure in the crust. It indicates that the distortion process of the upper crust is controlled by the middle and lower crust, and proves that the mantle uplifting is the major drive for the formation of the rift. The asymmetry between the MOHO and the fault sag resulted from a simple shear de formation in the early stage of the fault sag. The mirror symmetry between the MOHO and the sag is the result of the mantle adjustment after the Nenjiang movement. The presence of sandwich structure and red fluid bodies indicates that the basin possesses the geological condition for the high geothermal flow, and that there are storeroom and pathway for inorganic matters in the deep of the basin.